presentation title · thermal power plant (water consumption limit) water consumption i. all plants...

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Water Consumption in Thermal Power Plants


Industry Parameter Standards

Thermal Power Plant (Water consumption

limit)

Water consumption

I. All plants with Once Through Cooling (OTC) shallinstall Cooling Tower (CT) and achieve specificwater consumption up to maximum of3.5m3/MWh within a period of two years fromthe date of publication of this notification.

II. All existing CT-based plants reduce specific waterconsumption up to maximum of 3.5m3/MWhwithin a period of two years from the date ofpublication of this notification.

III.New plants to be installed after 1st January 2017shall have to meet specific water consumption upto maximum of 2.5 m3/MWh and achieve zerowaste water discharged.

New Specific Water Consumption Norms


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Effect on Tata Power


Plant & Unit

Description

Applicable

Norm

Current Status & Action Plan Remarks

5x830MW

Unit # 10 COD –

7th Mar 2012

Unit # 50 COD –

22 Mar 2013

OTC to CT

based cooling

water system

Detailed feasibility study is being

taken up. However, even with

cooling towers, meeting the

specific water consumption of 3.5m3/MWh is not possible.

Given the technical CoC

limitation of 1.5, it is technically

impossible for sea water based

plants to achieve the norm of 3.5

m3/MWh

(with COC of 1.5, the specific

water consumption achievable is

more than 8 m3/MWh)

Current Status and Path forward for CGPL – Unit 10 to 50


Current Status and Path forward for Trombay Unit 5

Plant & Unit

Description

Applicable

Norm


1x500MW

CoD – 25 Jan

1984.

Completed 32

years

OTC to CT

based cooling

water system

Implementation of cooling towers

is not feasible due to space constraints

• Station is planned within

0.27 acres/MW as against

CEA norm of 0.42 acres/MW

for coastal plants

• Condenser replacement reqd



Plant & Unit

Description

Applicable

Norm


1x500MW

CoD – 23rd Mar

1990.

Completed 26

years.

OTC to CT

based cooling

water system

Implementation of cooling towers

is not feasible due to space constraints

• Station is planned within

0.27 acres/MW as against

CEA norm of 0.42 acres/MW

for coastal plants.



Plant & Unit

Description

Applicable Norm Current Status & Action Plan Remarks

1x250MW

CoD – 29th

Mar 2008

OTC to CT based

cooling water

system

Installation of cooling towers may

be possible, it will not result in

reduction in sea water requirement

as operation of sea water based

FGD would be essential to meet

norms related to SO2 emissions,

which is presently draws water from CW outlet.

The min specific water

consumption achievable with

Cooling towers make up and

plant water requirement will be

higher than 8.m3/MWh.


Current Status and Path forward for Maithon Station

Plant & Unit

Description

Applicable Norm Current Status & Action

Plan

Remarks

2x525MW

CoD U1 – 1st Sept

2011

CoD U2 – 24th Jul

2012

Specific water consumption

upto maximum of

3.5m3/MWh

Meets new norms No action required.


Current Status and Path forward for Jojobera Unit # 1 to 3

Plant & Unit

Description

Applicable Norm Current Status &

Action Plan

Remarks

U1 Size – 67.5 MW

U2 Size – 120 MW

U3 Size – 120 MW

CoD U1 – 1st Apr

1997

CoD U2 – 1st Feb

2001

COD U3 – 1st Feb

2002

Specific water consumption

up to maximum of

3.5m3/MWh

Meets new norms No action required.


Current Status and Path forward for Jojobera Unit # 4 & 5

Plant & Unit

Description

Applicable Norm Current Status &

Action Plan

Remarks

U4 Size – 120 MW

U5 Size – 120 MW

CoD U4 – 23rd Nov

2005

CoD U5 - 27th Mar

2011

Specific water consumption upto

maximum of 3.5m3/MWh

Meets new norms No action

required.


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Conversion from Sea Water Based Once Through CW

system to Cooling Tower Based CW System


Comparison of Cooling Tower Technologies

Description NDCT IDCT

Layout Tower requires greater area due to

lower water loading

Tower requires smaller area

due to higher water loading

Part Load

Operation

Operates at design heat load. Can operate at various load

conditions

Volume of water

handled

Generally suitable for large water

flowsSuitable for all water flows

Facility to

enhance

capacity

Capacity cannot be enhanced once

the tower is built.

Capacity can be increased at a

later stage

Effect of

Relative

Humidity

Tower sizing is directly affected by

relative humidity of the inlet air

RH has very negligible effect

on performance once the inlet

WBT is fixed.

Maintenance Difficult to maintain due to access

restrictions.

Easier to maintain due to lower

heights.


Comparison of Cooling Tower Technologies

Description NDCT IDCT

Cost NDCT is at least 1.6-1.8 times in

construction cost.

Initial cost is much lower. Aux

power cost needs to be

considered for lifetime.

Aux Power

Consumption

No aux power consumption Typically about 0.5% of Unit

size.

Unequal water

and air loading

Possibility of unequal water and air

loadings exist due to very large size

of the tower which affects the

effectiveness.

IDCT sizes are limited to 20 to

22m, hence, unequal water

distribution phenomena does

not affect effectiveness.


Cost Estimates for Cooling Tower

Attributes Description

Capital Cost Estimated at about Rs 0.3 to 0.4 Crores / MW.

Aux power

consumption

Estimated at about additional 0.6% of station/Unit including additional

power for pump.

O&M cost per

annum

Estimated at about Rs 0.002 Cr/MW.


Challenges for Installation of CTs

Challenges Description

Layout • Plants which are 20-25 years old and have once through cooling

water system, no space had been envisaged for installation of CT.

• Approx area of 2 acres will be required for installation of CT for

500MW Unit. Additional land for electrical equipment, pump house,

fore-bay, chemical dosage facility etc will also be required..

• Even if, by any means, space required for installation of CTs is

identified, locating of CT w.r.t direction of wind, effect of mist on

switchyard, re-circulation etc may not be suitable.

• For 500MW Unit, the CW pipe of 3.2 metres dia is required. Routing

of such huge dia pipe within the existing under-ground facilities may

not be feasible without long outages of Unit.




CoC for Sea

water

Sea water has Total Dissolved Solid (TDS) concentration ranging from

35000 ppm to 47000 ppm. Max CoC achievable for sea water based

cooling towers is about 1.5.

Therefore even with installation of cooling towers, specific sea water

consumption for a 800MW along with plant water requirement will be

above 8m3/MWh and technically it is not possible meeting limitation of

3.5 m3/MWh.

Aux Power

Consumption

Installation of Cooling Tower will result into higher aux power

consumption.

Additional aux power consumption of approx. 0.5% to 0.7% of Unit

capacity is estimated.

Effect on

Existing

Condenser

Cooling Tower will require higher discharge head pump. This will subject

existing condenser to higher pressure compare to its present design

value warranting its replacement in case margins are not available.

Estimated outage time required more than 3 months.




Retrofit

issues

The plant electrical system will have to be augmented to provide the

additional auxiliary power required for cooling towers.

Modification to existing cooling water system is required, which will result

into station/unit outage.

Impact on Sea

water FGD

If cooling towers are to be installed with plants having OTC system with

sea water, the sea water based FGDs, which are most economical and

eco-friendly, will have to be shut or will not be feasible.


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Methods of Reduction of Specific Water Consumption for

Fresh Water Cooling tower based Stations


Methodologies for Reduction of Specific Water Consumption

Recycling and Reuse: Recycle and reuse of waste water shall be adopted to minimize

the fresh water consumption. In this philosophy, the waste water generated in one system is

reused in some other systems/applications wherever such quality of water is permissible to

use.



Sl.No Waste water CharacteristicsPossible use

or action

Remark

1. Cooling tower

blow down

Low TSS

Moderate TDS

High

temperature

Ash handling

Coal dust

suppression

2. Back wash water

from filtration unit

Moderate TSS

Low TDS

Recycled in

plant clarifier

3. Back wash from

side stream filter

of cooling tower

High TSS

Moderate TDS

Recycled in

plant clarifier

Need to be treated

in a sludge removal

system (sludge

clarifier, thickener

and dehydrator)

4. Floor wash Moderate TSS

Low TDS

Recycled in

ETP



Sl.No Waste water CharacteristicsPossible use or

action

Remark

5. Sewage Moderate TSS

Low TDS

High BOD

Gardening To be treated in

sewage treatment

plant and the clear

water can be reused

6. Regeneration waste

from DM plant

Low TSS

High TDS

Product water

can be used as

fresh water

To be treated in ZLD/

Reuse in ash slurry

preparation

Detailed study for the above options needs to carried out before adoption.

presentation title · thermal power plant (water consumption limit) water consumption i. all plants...

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